This invention relates in general to blades for use in surgical knives and, more specifically, to improved surgical blades for use in eye surgery, such as radial keratotomy.
A variety of different surgical blades have been developed over the years for use in different types of surgery. Conventional surgical blades have been made of steel and designed for different types of surgery, such as the blades described by Freedman in U.S. Pat. No. 4,185,634 for use in foot or hand surgery and the various surgical blade shapes described by Driest in U.S. Pat. No. 2,049,898 for use in general surgery.
As the ability to perform surgery on the eye has developed, in particular surgery of the cornea, a need for much smaller, sharper and more precise surgical blades followed. In radial keratotomy, it is often necessary to make a plurality of radial incisions in the cornea to a uniform depth. Typically, these incisions have been made using a fine knife having a pointed blade with the angle between blade edges being about 45.degree., as shown, for example, by Anis in U.S. Pat. No. 4,602,630. Similarly, a blade having a sharp point and an angle between blade edges of about 45.degree. is shown by Kramer et al in U.S. Pat. No. 4,688,570 for use with a template in performing radial keratotomy. More recently, diamond blades have come into use due to their small size and ability to retain a fine, sharp edge.
While the surgical blades of the prior art are generally effective when carefully used, they suffer from a number of drawbacks. The relatively wide angle between blade edges, typically 35.degree. to 45.degree., makes accurate plunging of the blade into corneal tissue to a precise depth at the start of an incision difficult. While it is generally preferred that the ends of an incision be approximately perpendicular to the surface of the eye, these blades leave sloping edges on at least one end. The pointed tips of these knives are much more fragile and susceptible to wear and damage if bumped against objects. Since these wide blades have a relatively wide blade portion in an incision, turning the blade precisely to form a number of parallel curved incisions, each with uniform radius, as is required when performing astigmatic surgery, is very difficult.
Thus, there is a continuing need for improved surgical blades for use in eye surgery and other precise surgery which permits the formation of precise incisions having ends more nearly vertical to the eye surface, allows precise formation of curved incisions and resists damage to the blade tip.